Air pollution poses an ongoing serious health risk in Shanghai as the average Air Quality Index here is seldom lower than 50 — the standard for good air. While eliminating the problem is pretty much impossible, there are things you can do to reduce exposure to 2.5 micron particles. A common misperception is that indoor air is always safe as 2.5 micron particles levels inside are commonly over the World Health Organization’s standard. Spending thousands of yuan on an expensive air purifier isn’t necessary to reduce exposure. You can make your own air purifier that costs less than 500 yuan (US$78.5). Thomas Talhelm shows us how.

Get clean air for less than 500 yuan

A basic household fan and HEPA filter (a mat of randomly arranged polyester fibers) will have more than 99 percent of particles below and above 0.3 microns from a room.

Make a DIY air purifier, invented by Talhelm, capable of removing 96 percent of 2.5 micron particles. It is similar to store bought filters and costs only 470 yuan. You need the following:Use the strap to fasten the filter to the fan to assemble your own “Cannon,” Talhelm’s name for it and get clean air without spending a wheelbarrow full of cash.

Next question: Is the DIY air purifier able to clean the air in an entire room?

Answering this question is more difficult because one needs a controlledenvironment (for example, one can’t walk in and out of the room during thetest), and one needs to test the air for a longer period of time.Thomas set up the particle counter on one side of his 13.5-square-meterbedroom and put the DIY filter on the opposite side of the room. Here’s whathis filter did in one hour:

And over the course of eight hours:

How well does the DIY air purifier perform compared to expensive air purifiers?

Thanks to kind souls who donated a BlueAir 203/270E (3,600 yuan), a Philips AC4072 (3,000 yuan), and an IQAir Health Pro (8,000 yuan) to Talhelm and his team, they have been able to test the DIY purifier against expensive brands in the same room for the same amount of time with the same particle counter.

To do that, his team ran 11 overnight tests with the BlueAir, nine tests with the Philips, and 11 tests with the IQAir. Talhelm calculated effectiveness as percent reduction in particulates from the room’s air. Other team members tested the air before turning on the air filter, and then set the particle counter to take hourly measurements of the air in the bedroom. He used the highest setting on each filter.

All of the filters significantly reduced particulates, but the 470-yuan “Cannon” removed as many particles as the best performing big brand. Among the brandsthere seems to be no relationship between price and particulate removal:

Ready to make you own air purifier? ClickHERE for more details about where to get the fan, filter and strap.